Impact resistant coating compositions

ABSTRACT

A curable coating composition includes: (a) a binder having a film-forming resin with at least two functional groups, and (ii) a curing agent reactive with the functional groups of the film-forming resin; and (b) solid vulcanized rubber particles that are unreactive with the binder. The curable coating composition is a solid particulate powder coating composition. Multi-layer coating systems and methods of preparing the curable coating composition are also included.

FIELD OF THE INVENTION

The present invention relates to impact resistant coating compositions,methods of preparing the coating compositions, and substrates at leastpartially coated with such compositions.

BACKGROUND OF THE INVENTION

Metallic substrates, such as cold-rolled steel found in springs andcoils, are susceptible to chipping, scratching, and other physicaldamage. To prevent or reduce such damage, an impact resistant coating istypically applied over the surface of the substrate or over a corrosionresistant primer that is first applied to the substrate. However, byincreasing the impact resistance of a coating, other desirableproperties, such as chemical resistance and Taber resistance, are oftenadversely effected.

Considerable efforts have been expended in developing topcoats thatreduce or prevent chipping, scratching, and other physical damage tometallic substrates. Although these coatings provide some degree ofimpact resistance and other desirable properties, they still exhibitsome drawbacks. For example, some of the currently available impactresistant coatings exhibit an undesirable appearance, while othercurrently available coatings exhibit poor impact resistance andcushioning around curvatures of non-planar substrates such as metallicsprings and coils.

In addition, some of the currently available impact resistant coatingsexhibit poor impact resistance at low temperatures around −40° C. Forinstance, some of the currently available impact resistant coatings thatinclude core-shell structures, thermoplastic resin blends, fibrousmaterials, and/or rubber adducts have been found to exhibit poor impactresistance at low temperatures around −40° C.

As such, it is desirable to provide improved impact resistant coatingsthat exhibit good impact resistance at low temperatures such astemperatures around −40° C.

SUMMARY OF THE INVENTION

The present invention is directed to a curable coating compositioncomprising: (a) a binder comprising (i) a film-forming resin comprisingat least two functional groups, and (ii) a curing agent reactive withthe functional groups of (i); and (b) solid vulcanized rubber particlesthat are unreactive with the binder. Further, the curable coatingcomposition is a solid particulate powder coating composition.

The present invention is also directed to a method of preparing acurable coating composition. The method includes mixing a combination ofsolid components to form a mixture comprising: a film-forming resincomprising at least two functional groups; a curing agent reactive withthe functional groups of the film-forming resin; and solid vulcanizedrubber particles unreactive with the film-forming resin and curingagent. The mixture is then melted and further mixed. The melted mixtureis cooled and ground to form a solid particulate curable powder coatingcomposition.

The present is further directed to a multi-layer coating systemcomprising: a first coating layer; and a second coating layer depositedover the first coating layer. The first and/or second coating layer isprepared from a curable coating composition comprising: (a) a bindercomprising (i) a film-forming resin comprising at least two functionalgroups, and (ii) a curing agent reactive with the functional groups of(i); and (b) solid vulcanized rubber particles that are unreactive withthe binder. Further, said curable coating composition that forms thefirst and/or second coating layer is a solid particulate powder coatingcomposition.

DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances. Further, in this application, the use of “a”or “an” means “at least one” unless specifically stated otherwise. Forexample, “a” film-forming resin, “a” curing agent, “a” vulcanized rubberparticle, and the like refer to one or more of any of these items.

As indicated, the present invention is directed to a curable coatingcomposition. As used herein, the terms “curable”, “cure”, and the like,as used in connection with a coating composition, means that at least aportion of the components that make up the coating composition arepolymerizable and/or crosslinkable. The curable coating composition ofthe present invention can be cured at ambient conditions, with heat, orwith other means such as actinic radiation. As used herein, “ambientconditions” refers to the conditions of the surrounding environment(e.g., the temperature, humidity, and pressure of the room or outdoorenvironment in which the substrate is located). The term “actinicradiation” refers to electromagnetic radiation that can initiatechemical reactions. Actinic radiation includes, but is not limited to,visible light, ultraviolet (UV) light, X-ray, and gamma radiation.

The curable coating composition of the present invention includes abinder. As used herein, a “binder” refers to a main constituent materialthat holds all components together upon curing of the curable coatingcomposition applied to a substrate. The binder includes one or more,such as two or more, film-forming resins. As used herein, a“film-forming resin” refers to a resin that can form a self-supportingcontinuous film on at least a horizontal surface of a substrate uponremoval of any diluents or carriers present in the composition or uponcuring. Further, as used herein, the term “resin” is usedinterchangeably with “polymer,” and the term polymer refers to oligomersand homopolymers (e.g., prepared from a single monomer species),copolymers (e.g., prepared from at least two monomer species),terpolymers (e.g., prepared from at least three monomer species), andgraft polymers.

The film-forming resins can include any of a variety of thermosettingfilm-forming resins known in the art. As used herein, the term“thermosetting” refers to resins that “set” irreversibly upon curing orcrosslinking, wherein the polymer chains of the polymeric components arejoined together by covalent bonds. This property is usually associatedwith a cross-linking reaction of the composition constituents ofteninduced, for example, by heat or radiation. Curing or crosslinkingreactions also may be carried out under ambient conditions. Once curedor crosslinked, a thermosetting resin will not melt upon the applicationof heat and is insoluble in solvents.

In some examples, the film-forming resins include thermoplastic resins.As used herein, the term “thermoplastic” refers to resins that includepolymeric components that are not joined by covalent bonds and, thereby,can undergo liquid flow upon heating and are soluble in solvents.

Alternatively, the curable coating composition of the present inventionis substantially free, essentially free, or completely free of athermoplastic resin. The term “substantially free of a thermoplasticresin” means that the curable coating composition contains less than1000 parts per million by weight (ppm) of a thermoplastic resin based onthe total weight of the composition, “essentially free of athermoplastic resin” means that the curable coating composition containsless than 100 ppm of a thermoplastic resin based on the total weight ofthe composition, and “completely free of a thermoplastic resin” meansthat the curable coating composition contains less than 20 parts perbillion by weight (ppb) of a thermoplastic resin based on the totalweight of the composition, including absence of a thermoplastic resin.

Non-limiting examples of suitable film-forming resins include(meth)acrylate resins, polyurethanes, polyesters, polyamides,polyethers, polysiloxanes, epoxy resins, vinyl resins, copolymersthereof, and combinations thereof. As used herein, “(meth)acrylate” andlike terms refers both to the acrylate and the correspondingmethacrylate. Further, the film-forming resins can have any of a varietyof functional groups including, but not limited to, carboxylic acidgroups, amine groups, epoxide groups, hydroxyl groups, thiol groups,carbamate groups, amide groups, urea groups, isocyanate groups(including blocked isocyanate groups), and combinations thereof.

As indicated, the resin used to form the binder can include, but is notlimited to, an epoxy resin. The epoxy resin can comprise at least twoepoxide functional groups. The epoxide functional groups can be terminaland/or pendant on the polymer chain. As used herein, a “pendant group”refers to a functional group that is attached to and extends out fromthe backbone of a polymer. The epoxy resin can also include any of theadditional functional groups previously described. For example, theepoxy resin can include at least one hydroxyl group. The hydroxylgroups, as well as any of the other additional functional groups, can beterminal and/or pendant on the polymer chain. Non-limiting examples ofepoxy resins include, but are not limited to, diglycidyl ethers ofbisphenol A, polyglycidyl ethers of polyhydric alcohols, polyglycidylesters of polycarboxylic acids, and combinations thereof. Non-limitingexamples of suitable epoxy resins are also commercially available fromNanYa Plastics under the trade name NPES-903, and from Hexion under thetrade names EPON™ 2002 and EPON 2004™.

The epoxy resin can have an equivalent weight of at least 500 or atleast 700. The epoxy resin can also comprise an equivalent weight of upto 1000 or up to 5100. The epoxy resin can comprise an equivalent weightrange within the range of 500 to 5100 or from 700 to 1000. As usedherein, “equivalent weight” refers to the average weight molecularweight of a resin divided by the number of functional groups. As such,the equivalent weight of the epoxy resin is determined by dividing theaverage weight molecular weight of the epoxy resin by the total numberof epoxide groups and any other optional functional groups that are notan epoxide. Further, the average weight molecular weight is determinedby gel permeation chromatography relative to linear polystyrenestandards of 800 to 900,000 Daltons as measured with a Waters 2695separation module with a Waters 410 differential refractometer (RIdetector). Tetrahydrofuran (THF) is used as the eluent at a flow rate of1 ml min-1, and two PLgel Mixed-C (300×7.5 mm) columns is used forseparation.

The binder used to form the coating composition of the present inventioncan also include two or more epoxy resins. For example, the binder caninclude at least two separate and distinct epoxy resins in which eachepoxy resin independently comprises at least two epoxide functionalgroups and, optionally, any of the other functional groups previouslydescribed, such as one or more hydroxyl groups. The multiple epoxyresins can have the same or different equivalent weights. For instance,a first epoxy resin can have an equivalent weight that is greater thanan equivalent weight of a second epoxy resin.

When two separate epoxy resins are used with the coating composition ofthe present invention, the second epoxy resin can comprise an equivalentweight of at least 500 or at least 700. The second epoxy resin can alsocomprise an equivalent weight of up to 1000 or up to 5000. The secondepoxy resin can comprise an equivalent weight range within the range of500 to 5000 or from 700 to 1000.

Further, the first epoxy resin can comprise an equivalent weight of atleast 800 or at least 900. The first epoxy resin can also comprise anequivalent weight of up to 5100 or up to 1100. The first epoxy resin cancomprise an equivalent weight range within the range of 800 to 5100 orfrom 900 to 1100.

The film-forming resins used to form the binder can comprise a glasstransition temperature (Tg) of at least 35° C. or at least 40° C. The Tgis determined using differential scanning calorimetry (DSC).

The coating composition of the present invention can also comprise atleast 15 weight %, at least 30 weight %, at least 50 weight %, at least60 weight % or at least 75 weight % of one or more film-forming resins,based on the total solids weight of the coating composition. The coatingcomposition of the present invention can comprise up to 90 weight % orup to 93 weight % of one or more film-forming resins, based on the totalsolids weight of the coating composition. The coating composition of thepresent invention can further include a range such as from 15 weight %to 93 weight %, or from 50 weight % to 93 weight %, or from 60 weight %to 90 weight % of one or more film-forming resins, based on the totalsolids weight of the coating composition.

As previously indicated, any of the ranges recited herein include any ofthe sub-ranges contained within such ranges.

The binder can also include a curing agent that is reactive with thefunctional groups of the film-forming resins. As used herein, a “curingagent” refers to a chemical compound that is capable of reacting with achemical group on a resin to cure or crosslink the resin material.Non-limiting examples of curing agents include phenolic compounds suchas phenolic hydroxyl functional compounds, epoxy compounds, triglycidylisocyanurate, beta-hydroxy (alkyl) amides, alkylated carbamates,isocyanates, polyacids, anhydrides, organometallic acid-functionalmaterials, polyamines, polyamides, polyfunctional polyols, aminoplasts,uretdiones such as polyuretdiones, boron trifluoride complexes, andcombinations thereof. The curing agent is not so limited and can includeany curing agent that is reactive with one or more functional groups onthe film-forming resins.

In some examples, the binder of the present invention can include anepoxy resin having at least two epoxide functional groups and a curingagent that is reactive with the epoxide groups of the epoxy resin. Thecuring agent that is reactive with the epoxy resin can include one ormore, such as two or more, of the previously described curing agentsthat are reactive with epoxide groups. For example, the curing agent cancomprise a phenolic hydroxyl functional compound. A non-limiting exampleof a suitable phenolic hydroxyl functional curing agent is commerciallyavailable from Hexion under the trade name EPIKURE™ P-201 and P-202.Other examples of suitable curing agents that are reactive with theepoxide groups of the epoxy resins are also disclosed in column 7, lines16 to 35 of U.S. Pat. No. 6,521,706, which is incorporated by referenceherein.

As indicated, the binder can include multiple curing agents that arereactive with the same or different functional groups on thefilm-forming resins. For example, the binder can include: (1) an epoxyresin that comprises at least two epoxide groups and at least onehydroxyl functional group; and (2) at least two curing agents in which afirst curing agent is reactive with the epoxide functional groups and asecond curing agent that is reactive with the hydroxyl group. In someexamples, the second curing agent can be chosen to react with the atleast one hydroxyl group on the resin to form a urethane linkage. Suchcuring agents include, but are not limited to, isocyanates, uretdiones,and mixtures thereof. The second curing agent can also be chosen toreact with the functional groups formed from a reaction between thefirst curing agent and the epoxide functional groups.

The coating composition of the present invention can comprise at least 3weight %, at least 10 weight %, or at least 15 weight % of one or morecuring agents, based on the total solids weight of the coatingcomposition. The coating composition of the present invention cancomprise up to 35 weight % or up to 30 weight % of one or more curingagents, based on the total solids weight of the coating composition. Thecoating composition of the present invention can further include a rangesuch as from 3 weight % to 35 weight %, or from 5 weight % to 32 weight%, or from 10 weight % to 30 weight %, or from 15 weight % to 30 weight% of one or more curing agents, based on the total solids weight of thecoating composition.

Further, the binder that is used to form the curable coating compositionof the present invention can be a solid. As such, the film-formingresins and curing agents reactive with the film-forming resins that makeup the binder can be in solid form. It is appreciated that any of thecomponents that form the binder can be provided initially as a liquidand/or a dispersion and then processed into a solid using techniquesknown in the art.

The binder of the present invention can comprise at least 15 weight %,at least 30 weight %, at least 50 weight %, at least 60 weight %, or atleast 75 weight %, based on the total solids weight of the coatingcomposition. The binder of the present invention can comprise up to 90weight %, or up to 93 weight %, or up to 96 weight %, based on the totalsolids weight of the coating composition. The binder of the presentinvention can further include a range such as from 15 weight % to 96weight %, or from 50 weight % to 96 weight %, or from 60 weight % to 96weight %, or from 75 weight % to 90 weight %, based on the total solidsweight of the coating composition.

The curable coating composition of the present invention also includesvulcanized rubber particles that are unreactive with the binder. As usedherein, a “vulcanized rubber particle” refers to a particle made of anelastomeric material that includes bonds that crosslink the polymerchains that make up the elastomeric material. For example, thevulcanized rubber particles can be crosslinked through sulfur bonds,through free radical crosslinking such as with peroxides, with metaloxides, with allylic chlorine containing compounds, withphenol-formaldehyde resins, with p-benzoquinonedioxime, or combinationsthereof. The vulcanized rubber particle can also be prepared from avariety of elastomeric materials. Non-limiting examples of suitablerubbers include nitrile rubber, butyl rubber, silicone rubber, ethylenepropylene rubber, ethylene propylene diene terpolymer rubber, styrenebutadiene rubber, natural rubber, polybutadiene, or combinationsthereof.

The vulcanized rubber particles can be obtained from recycled rubbermaterials. For example, the vulcanized rubber particles used with thecurable coating composition of the present invention can be obtainedfrom recycled tires. As a result, the vulcanized rubber particles caninclude additional components such as carbon black and others fillerstypically found in the rubber material of tires.

The vulcanized rubber particles can comprise various shapes and sizes.For instance, the vulcanized rubber particles can comprise an averageparticle size of at least 10 microns, at least 15 microns, or at least25 microns. The vulcanized rubber particles can comprise an averageparticle size of up to 85 microns, up to 80 microns, or up to 75microns. The vulcanized rubber particles can comprise an averageparticle size range of 10 microns to 85 microns, 15 microns to 80microns, or 25 microns to 75 microns. As used herein, “average particlesize” refers to the mean (average) particle size of the total amount ofparticles in a sample as determined by a Beckman-Coulter LS™ 13 320Laser Diffraction Particle Size Analyzer following the instructionsdescribed in the Beckman-Coulter LS™ 13 320 manual. Further, theparticle size range of the total amount of particles in a sample used todetermine the average particle size can comprise a range of from 5microns to 175 microns, or from 5 microns to 110 microns, or from 5microns to 90 microns, which is also determined with a Beckman-CoulterLS™ 13 320 Laser Diffraction Particle Size Analyzer following theinstructions described in the Beckman-Coulter LS™ 13 320 manual.

The particle sizes previously described can be obtained by grindingvulcanized rubber materials such as by grinding recycled rubbermaterials. The ground vulcanized rubber with the desired particle sizecan be prepared by any method known to those skilled in the art forachieving such small particle sizes. In some examples, the vulcanizedrubber particles are prepared at the desired particle size usingcryogenic grinding techniques. Non-limiting examples of methods forpreparing vulcanized rubber with the desired particle size are alsodescribed in column 6, lines 9 to 33 of U.S. Pat. No. 6,521,706, whichis incorporated by reference herein.

The vulcanized rubber particles can have a glass transition temperature(Tg) of less than −40° C. The vulcanized rubber particles can also havea Tg of less than −45° C., or less than −50° C. The Tg is determinedusing DSC as previously described. The vulcanized rubber particles cancomprise a combination of particles with different Tg's. For instance,the curable coating composition can include vulcanized rubber particlesthat independently comprise any of the Tg's previously described.

Further, the vulcanized rubber particles can comprise functional groupswith the proviso that they do not react with the components that formthe binder. Therefore, the vulcanized rubber particles are unreactivewith the film-forming resins and curing agents that form the binder. Thefunctional vulcanized rubber particles can comprise, but are not limitedto, any of the functional groups previously described as regards to thefilm-forming resin with the proviso that the functional groups areunreactive with the functional groups found on the film-forming resinsand curing agents of the binder. The vulcanized rubber particles arealso unreactive with any of the other components used with the curablecoating composition of the present invention. Because the vulcanizedrubber particles are unreactive with the other components of the curablecoating composition, the vulcanized rubber particles will not react withthese components to form an adduct, a core-shell structure, or any othercovalently bonded arrangement. In some examples, the coating compositionof the present invention is free of elastomeric materials, such as therubber particles, that form bonds with the resins and curing agents.

The vulcanized rubber particles that are used with the curable coatingcomposition of the present invention can also be a solid. As such, thevulcanized rubber particles can be formed from a solid elastomericmaterial including, but not limited to, a solid recycled vulcanizedrubber material. In some examples, the solid vulcanized rubber particlesare a solid particulate powder. For example, the vulcanized rubberparticles can comprise a powder produced from recycled rubber materialas defined by ASTM D5603-01(2015), which is incorporated by referenceherein in its entirety.

The coating composition of the present invention can comprise at least 1weight %, at least 5 weight %, or at least 10 weight % of vulcanizedrubber particles, based on the total solids weight of the coatingcomposition. The coating composition of the present invention can alsocomprise up to 40 weight %, up to 25 weight %, or up to 20 weight % ofvulcanized rubber particles, based on the total solids weight of thecoating composition. The coating composition of the present inventioncan further comprise a range such as from 1 weight % to 40 weight %, orfrom 5 weight % to 25 weight %, or from 10 weight % to 20 weight % ofvulcanized rubber particles, based on the total solids weight of thecoating composition.

It was found that the addition of unreactive vulcanized rubber particlesimproves the impact resistance of coatings formed from the curablecoating compositions of the present invention. The coatings also exhibitother desirable properties, such as good flexibility, appearance, Taberresistance, chip resistance, and chemical resistance.

The curable coating composition can also include pigment particles. Asused herein, a “pigment particle” refers to a particle that are used toimpart color in a coating composition. The term “colorant” is usedinterchangeably with the term “pigment particle.” Non-limiting examplesof pigment particles can include those used in the paint industry and/orlisted in the Dry Color Manufacturers Association (DCMA). Examplepigments and/or pigment compositions include, but are not limited to,carbazole dioxazine crude pigment, azo, monoazo, diazo, naphthol AS,salt type (flakes), benzimidazolone, isoindolinone, isoindoline andpolycyclic phthalocyanine, quinacridone, perylene, perinone,diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine,triarylcarbonium, quinophthalone pigments, diketo pyrrolo pyrrole red(“DPPBO red”), carbon black, certain metal oxides, and mixtures thereof.

The coating composition of the present invention can include from 0.25weight % to 50 weight %, or from 0.5 weight % to 50 weight %, or from 1weight % to 40 weight %, or from 5 weight % to 30 weight % of one ormore pigment particles, based on the total solids weight of the coatingcomposition.

Other non-limiting examples of materials that can be used with thecoating compositions of the present invention include plasticizers,fillers including, but not limited to, talcs, micas, wollastonite,graphite, calcium carbonate, micaceous iron oxide, barium sulfate,clays, anti-oxidants, flow and surface control agents, thixotropicagents, slip aids, catalysts, reaction inhibitors, texturizers, andother customary auxiliaries.

Particularly useful fillers that can be used with the curable coatingcompositions of the present invention include platy inorganic fillers,needle-shaped inorganic fillers, or combinations thereof. As usedherein, a “platy inorganic filler” refers to an inorganic material inthe platy form. The term “platy” refers to a structure in which onedimension is substantially smaller than the two other dimensions of thestructure resulting in a flat type appearance. The platy inorganicfillers are generally in the form of stacked lamellae, sheets,platelets, or plates with a relatively pronounced anisometry. The term“needle-shaped inorganic filler” refers to a structure in which onedimension is substantially larger than the other two dimensions of thestructure resulting in a needle type appearance. The platy inorganicfiller and needle-shaped inorganic filler can further improve the impactperformance of the resulting coating.

The platy and needle-like inorganic fillers can have a high aspectratio. Suitable high aspect ratio platy and needle-like inorganicfillers include, but are not limited to, vermiculite, mica, talc,wollastonite, chlorite, metal flakes, platy clays, and platy silicas.Such fillers typically have, but are not limited to, diameters of 1 to100 microns, 2 to 25 microns, or 2 to 50 microns. The aspect ratio ofsuch fillers can be at least 5:1, such as at least 10:1 or 20:1. Forexample, mica flakes may have an aspect ratio of 20:1, talc may have anaspect ratio of 10:1 to 20:1, and vermiculite may have an aspect ratioof from 200:1 to 10,000:1.

In some examples, the curable coating composition of the presentinvention is substantially free, essentially free, or completely free offiberglass. As used herein, the term “fiberglass” refers to continuousstrands of glass fibers that have been extruded into fine filaments.Further, the term “substantially free of fiberglass” means that thecurable coating composition contains less than 1000 parts per million byweight (ppm) of fiberglass based on the total weight of the composition,“essentially free of fiberglass” means that the curable coatingcomposition contains less than 100 ppm of fiberglass based on the totalweight of the composition, and “completely free of fiberglass” meansthat the curable coating composition contains less than 20 parts perbillion by weight (ppb) of fiberglass based on the total weight of thecomposition. In some examples, the absence of fiberglass in the curablecoating compositions helps provide a cured coating with a better visualappearance and/or impact resistance.

The previously described binder, vulcanized rubber particles, andoptional additional components can be combined to form a powder coatingcomposition. A “powder coating composition” refers to a coatingcomposition embodied in solid particulate form as opposed to liquidform. Thus, the previously described components can be combined to forma curable solid particulate powder coating composition. For instance,the binder, vulcanized rubber particles, and optional additionalcomponents can be combined to form a curable solid particulate powdercoating composition that is free flowing. As used herein, the term “freeflowing” with regard to curable solid particulate powder coatingcompositions of the present invention, refers a curable solidparticulate powder composition having a minimum of clumping oraggregation between individual particles.

The curable solid particulate powder coating composition can be preparedby mixing the binder, vulcanized rubber particles unreactive with thebinder, and optional additional components in solid form. It will beappreciated that some optional additives can be provided as a liquid ordispersion and formed into a solid material. The solid components aremixed such that a homogenous mixture is formed. The solid components canbe mixed using art-recognized techniques and equipment such as with aPrism high speed mixer for example. The homogenous mixture is thenmelted and further mixed. The mixture can be melted with a twin screwextruder or a similar apparatus known in the art. During the meltingprocess, the temperatures will be chosen to melt mix the solidhomogenous mixture without curing the mixture. In some examples, thehomogenous mixture can be melt mixed in a twin screw extruder with thefirst zone set to a temperature of 40° C. to 60° C., such as from 45° C.to 55° C., and with the second, third, and fourth zones set to atemperature of 70° C. to 110° C., such as from 75° C. to 100° C. Aftermelt mixing, the mixture is cooled and re-solidified. The re-solidifiedmixture is then ground such as in a milling process to form a solidparticulate curable powder coating composition. The re-solidifiedmixture can be ground to any desired particle size. For example, in anelectrostatic coating application, the re-solidified mixture can beground to an average particle size of at least 10 microns or at least 20microns and up to 100 microns as determined with a Beckman-Coulter LS™13 320 Laser Diffraction Particle Size Analyzer following theinstructions described in the Beckman-Coulter LS™ 13 320 manual.Further, the particle size range of the total amount of particles in asample used to determine the average particle size can comprise a rangeof from 1 micron to 200 microns, or from 5 microns to 180 microns, orfrom 10 microns to 150 microns, which is also determined with aBeckman-Coulter LS™ 13 320 Laser Diffraction Particle Size Analyzerfollowing the instructions described in the Beckman-Coulter LS™ 13 320manual.

The curable coating composition of the present invention can be appliedto a wide range of substrates known in the coatings industry. Forexample, the coating compositions of the present invention can beapplied to automotive substrates, industrial substrates, aerocraft andaerocraft components, packaging substrates, wood flooring and furniture,apparel, electronics, including housings and circuit boards, glass andtransparencies, sports equipment, including golf balls, and the like.These substrates can be, for example, metallic or non-metallic. Metallicsubstrates include, but are not limited to, tin, steel (includingelectrogalvanized steel, cold rolled steel, hot-dipped galvanized steel,among others), aluminum, aluminum alloys, zinc-aluminum alloys, steelcoated with a zinc-aluminum alloy, and aluminum plated steel.Non-metallic substrates include polymeric, plastic, polyester,polyolefin, polyamide (nylon), cellulosic, polystyrene, polyacrylic,poly(ethylene naphthalate), polypropylene, polyethylene, EVOH,polylactic acid, other “green” polymeric substrates,poly(ethyleneterephthalate) (PET), polycarbonate,polycarbonate/acrylonitrile-butadiene styrene copolymer blend (PC/ABS),wood, veneer, wood composite, particle board, medium density fiberboard,cement, stone, glass, paper, cardboard, textiles, leather, bothsynthetic and natural, and the like.

The curable coating compositions of the present invention areparticularly beneficial when applied directly to a metallic substrate ora pretreated metallic substrate. For example, the curable coatingcompositions of the present invention are particularly beneficial whenapplied to metallic springs or coils such as cold-rolled steel coils,galvanized steel coils, and aluminum coils.

The curable coating compositions of the present invention can be appliedby any means standard in the art, such as spraying, electrostaticspraying, and the like. The coatings formed from the coatingcompositions of the present invention can be applied to a dry filmthickness of 2 to 1800 microns, 50 to 1000 microns, or 300 to 800microns.

The coating composition can be applied to a substrate to form amonocoat. As used herein, a “monocoat” refers to a single layer coatingsystem that is free of additional coating layers. Thus, the coatingcomposition can be applied directly to a substrate and cured to form asingle layer coating, i.e. a monocoat. When the curable coatingcomposition is applied to a substrate to form a monocoat, the coatingcomposition can include additional components to provide other desirableproperties. For example, the curable coating composition can alsoinclude an inorganic component that acts as a corrosion inhibitor. Asused herein, a “corrosion inhibitor” refers to a component such as amaterial, substance, compound, or complex that reduces the rate orseverity of corrosion of a surface on a metal or metal alloy substrate.The inorganic component that acts as a corrosion inhibitor can include,but is not limited to, an alkali metal component, an alkaline earthmetal component, a transition metal component, or combinations thereof.

The term “alkali metal” refers to an element in Group 1 (InternationalUnion of Pure and Applied Chemistry (IUPAC)) of the periodic table ofthe chemical elements, and includes, e.g., cesium (Cs), francium (Fr),lithium (Li), potassium (K), rubidium (Rb), and sodium (Na). The term“alkaline earth metal” refers to an element of Group 2 (IUPAC) of theperiodic table of the chemical elements, and includes, e.g., barium(Ba), beryllium (Be), calcium (Ca), magnesium (Mg), and strontium (Sr).The term “transition metal” refers to an element of Groups 3 through 12(IUPAC) of the periodic table of the chemical elements, and includes,e.g., titanium (Ti), Chromium (Cr), and zinc (Zn), among various others.

Specific non-limiting examples of inorganic components that act as acorrosion inhibitor include magnesium oxide, magnesium hydroxide,magnesium carbonate, magnesium phosphate, magnesium silicate, zincoxide, zinc hydroxide, zinc carbonate, zinc phosphate, zinc silicate,zinc dust, and combinations thereof.

Alternatively, the curable coating composition can be applied over afirst coating layer deposited over a substrate to form a multi-layercoating system. For example, a coating composition can be applied to asubstrate as a primer layer and the curable coating compositionpreviously described can be applied over the primer layer as a topcoat.As used herein, a “primer” refers to a coating composition from which anundercoating may be deposited onto a substrate in order to prepare thesurface for application of a protective or decorative coating system. Abasecoat can also be used with the multi-layer coating system. A“basecoat” refers to a coating composition from which a coating isdeposited onto a primer and/or directly onto a substrate, optionallyincluding components (such as pigments) that impact the color and/orprovide other visual impact, and which may be overcoated with aprotective and decorative topcoat.

In some examples, a first coating layer, such as a primer layer, can beapplied directly over a substrate to protect the substrate fromcorrosion and the curable coating composition previously described canbe applied over the first coating layer to at least provide impactresistance. As such, the first coating layer can comprise a film-formingresin including, but not limited to, any of the film-forming resinspreviously described, optionally, a curing agent including, but notlimited to, any of the curing agents previously described, an inorganiccomponent that acts as a corrosion inhibitor, and, optionally, otheradditives previously described. The inorganic component that acts as acorrosion inhibitor and which can be used with the first coating layercan include, but is not limited to, any of the inorganic corrosioninhibiting components previously described.

It is appreciated that the curable coating composition comprising thesolid vulcanized rubber particles can be used as the first coating layerin a multi-layer coating system. When used as a first layer, the curablecoating composition can include additional components such as theinorganic corrosion inhibiting components previously described. Thesecond coating layer applied over the first coating layer can include acoating prepared from the curable coating composition comprising thevulcanized rubber particles. The second coating layer can also beprepared from a different coating composition such as those known in theart.

It was found that the curable coating compositions of the presentinvention provide good impact resistance, flexibility, and visualappearance when applied to a metallic substrate and cured to form acoating. The curable coating compositions were also found to providegood impact resistance, flexibility, and visual appearance when used ina multi-layer coating system as a topcoat.

The following examples are presented to demonstrate the generalprinciples of the invention. The invention should not be considered aslimited to the specific examples presented. All parts and percentages inthe examples are by weight unless otherwise indicated. Further, withrespect to the Tables listed in the following Examples, the abbreviation“Comp. Ex.” means “Comparative Example” and the abbreviation “Ex.” means“Example.”

EXAMPLES 1-7 Preparation of Curable Coating Compositions

Seven (7) curable coating compositions were prepared from the componentslisted in Table 1.

TABLE 1 Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex.6 Ex. 7 Component (gram) (gram) (gram) (gram) (gram) (gram) (gram)NPES-903 ¹ 76.15 — 39.03 31.27 48.95 64.51 60.62 EPON ™ 2004 ² — 80.0739.03 — — — — HyPox ™ RK84L ³ — — — 50.09 — — — RESTFLOW ® PL-200A ⁴1.00 1.00 1.00 1.00 1.00 1.00 1.00 Uraflow B ⁵ 0.50 0.50 0.50 0.50 0.500.50 0.50 DYHARD ® MI-FF ⁶ 0.22 0.23 0.22 0.23 0.14 0.17 0.17 REGAL ®660 ⁷ 0.50 0.50 0.50 0.50 0.50 0.50 0.50 EPIKURE ™ P-202 ⁸ 21.63 17.7019.72 16.41 13.91 18.32 17.22 Micronized/vulcanized — — — — 15.00 15.0015.00 rubber particles ⁹ CRELAN ® EF 403 ¹⁰ — — — — — — 5.00 Milledfiber glass (less — — — — 20.00 — — than 2 mm particle size) ¹ An epoxyresin based on diglycidyl ether of bisphenol A having an equivalentweight of about 700 to 750, commercially available from NanYa Plastics.² An epoxy resin based on diglycidyl ether of bisphenol A (formed frombisphenol A and epichlorohydrin) having an equivalent weight of about875 to 975, commercially available from Hexion. ³ An adduct of soliddiglycidyl ether of Bisphenol A and a liquid rubber, commerciallyavailable from Emerald Performance Materials. ⁴ Acrylic/silica flow andleveling control agent, commercially available from Estron Chemical. ⁵Benzoin, commercially available from Mitsubishi Chemical Corp. ⁶ Anaccelerator for elevated temperature curing of epoxy resin formulations,commercially available from ALZ Chem. ⁷ Carbon black, commerciallyavailable from Cabot. ⁸ Phenolic hydroxyl terminated solid flaked curingagent containing an accelerator, commercially available from Hexion. ⁹Free flowing black powder produced from recycled vulcanized rubbermaterial as defined by ASTM D5603-01(2015) with an average particle sizerange of 10 microns to 85 microns, as determined with a Beckman-CoulterLS ™ 13 320 Laser Diffraction Particle Size Analyzer following theinstructions described in the Beckman-Coulter LS ™ 13 320 manual. ¹⁰Cycloalipatic polyuretdione without blocking agent, commerciallyavailable from Bayer.

Each of the components listed in Table 1 for Examples 1-7 were weighedin a container and mixed in a prism high speed mixer for 30 seconds at3500 RPM to form a dry homogeneous mixture. The mixture was then meltmixed in a Werner Pfleiderer 19mm twin screw extruder with an aggressivescrew configuration and a speed of 500 RPM. The first zone was set at50° C., and the second, third, and fourth zones were set at 80° C. Thefeed rate was such that a torque of 50-60% was observed on theequipment. The mixtures were dropped onto a set of chill rolls to cooland re-solidify the mixtures into solid chips. The chips were milled ina Mikro ACM®-1 Air Classifying Mill to obtain an average particle sizeof 10 microns to 100 microns. The resulting coating compositions foreach of Examples 1-7 were solid particulate powder coating compositionsthat were free flowing.

EXAMPLE 8 Application of Solid Particulate Powder Coatings

A first powder coating composition comprising an epoxy resin, a curingagent reactive with the epoxy resin, and a zinc component was appliedover several high tensile strength steel coil springs. The first powdercoating composition was applied at a thickness of 25 microns to 100microns onto a pre-heated substrate at 375° F. for about 25 to 35minutes to form a first coating layer. Each of the solid particulatepowder coating compositions of Examples 1-7 were then electrostaticallysprayed over the first coating layer while the first coating layer wasstill hot. The solid particulate powder coating compositions of Examples1-7 were applied at a thickness of 350 microns to 1000 microns and bakedfor about 35 minutes at 375° F.

EXAMPLE 9 Evaluation of Impact Resistance

Each of the multi-layer coatings prepared from the compositions ofExamples 1-7 were evaluated for impact resistance and final dry filmthickness of the primer plus topcoat. Film build was measured with a dryfilm gauge from Elcometer, model number 415. The impact resistance ofeach coating system was determined according to ISO 4532 at −40° C. The“pistol” testing instrument was set to a load of 90N. The coil springswere left in the freezer at −40° C. for 24 hours and then removed andimpacted at a 90° angle to the coil springs surfaces within 30 secondsof being removed from the freezer.

Each of the coatings were tested various times for impact resistanceusing the test previously described. The coatings that exhibitedphysical damage, such as chipping, were recorded as a failure. Thepercent (%) failure was then determined based on the total number oftests administered for each type of coating. The results are shown inTable 2.

TABLE 2 Testing Comp. Comp. Comp. Comp. Comp. Ex. Ex. Property Ex. 1 Ex.2 Ex. 3 Ex. 4 Ex. 5 6 7 Average dry 638 816 663 893 740 689 892 filmthickness based on 6 readings (μm) Powder Fine Fine Fine Gelled FineFine Fine Stability at pow- pow- pow- pow- pow- pow- −40° C. after derder der der der der 2 Days % Failure 40% 57% 58% 100% 100% 11% 3%

As shown in Table 2, the coatings prepared from the coating compositionsof Examples 6 and 7, which included a topcoat according to the presentinvention, exhibited the best impact resistance with the lowest failurerates. Further, the coatings prepared from the coating compositions ofComparative Example 4, which included an adduct of solid diglycidylether of Bisphenol A and a liquid rubber, and Comparative Example 5,which included milled fiberglass, both exhibited 100% failure.

The present invention also includes the following aspects.

Aspect 1: A curable coating composition comprising: (a) a bindercomprising: (i) a film-forming resin comprising at least two functionalgroups; and (ii) a curing agent reactive with the functional groups of(i); and (b) solid vulcanized rubber particles unreactive with thebinder, wherein the curable coating composition is a solid particulatepowder coating composition.

Aspect 2: The curable coating composition of aspect 1, wherein thefilm-forming resin has a glass transition temperature (Tg) of at least35° C. such as at least 40° C.

Aspect 3: The curable coating composition of any one of aspects 1 or 2,wherein the film-forming resin comprises an epoxy resin having at leasttwo epoxide groups and wherein the curing agent is reactive with theepoxide groups.

Aspect 4: The curable coating composition of aspect 3, wherein the epoxyresin further comprises at least one hydroxyl group.

Aspect 5: The curable coating composition of aspect 4, furthercomprising a second curing agent that is reactive with the hydroxylgroup.

Aspect 6: The curable coating composition of any one of aspects 3 to 5,wherein the epoxy resin has an equivalent weight of from 500 to 5100.

Aspect 7: The curable coating composition of any one of aspects 1 or 2,wherein the curable coating composition comprises at least a first epoxyresin and a second epoxy resin that each independently comprise at leasttwo epoxide groups and wherein the curing agent is reactive with theepoxide groups, wherein the first epoxy resin has an equivalent weightthat is greater than the equivalent weight of the second epoxy resin.

Aspect 8: The curable coating composition of any one of aspects 7 or 5,wherein the first and/or second epoxy resin further comprise at leastone hydroxyl group.

Aspect 9: The curable coating composition of any one of aspects 7 or 8,wherein the first epoxy resin has an equivalent weight of from 800 to5100 such as from 900 to 1100 and the second epoxy resin has anequivalent weight of from 500 to 5000 such as from 700 to 1000.

Aspect 10: The curable coating composition of any one of aspects 1 to 9,wherein the solid vulcanized rubber particles have an average particlesize of up to 85 microns such as from 10 microns to 85 microns, or form15 microns to 80 microns, or from 25 microns to 75 microns.

Aspect 11: The curable coating composition of any one of aspects 1 to10, wherein the solid vulcanized rubber particles comprise up to 40weight % of the coating composition such as from 1 to 40 weight %,preferably from 5 to 25 weight %, and more preferably from 10 to 20weight %, based on the total solid weight of the coating composition.

Aspect 12: The curable coating composition of any one of aspects 1 to11, wherein the vulcanized rubber particles have a glass transitiontemperature (Tg) of less than −40° C. such as less than −45° C., or lessthan −50° C.

Aspect 13: The curable coating composition of any one of aspects 1 to12, further comprising pigment particles.

Aspect 14: The curable coating composition of any one of aspects 1 to13, wherein the coating composition contains less than 1000 parts permillion by weight (ppm) of fiberglass, preferably less than 100 ppm offiberglass, based on the total weight of the composition, and morepreferably is completely free of fiberglass.

Aspect 15: The curable coating composition of any one of aspects 1 to14, further comprising a platy inorganic filler, a needle-shapedinorganic filler, or a combination thereof.

Aspect 16: The curable coating composition of any one of aspects 1 to15, wherein the coating composition contains less than 1000 parts permillion by weight (ppm) of a thermoplastic resin, preferably less than100 ppm of a thermoplastic resin, based on the total weight of thecomposition, and more preferably is completely free of a thermoplasticresin.

Aspect 17: The curable coating composition of any one aspects 1 to 16,wherein the coating composition further comprises an inorganic corrosioninhibiting component comprising a transition metal component, an alkalimetal component, an alkaline earth metal component, or combinationsthereof.

Aspect 18: The curable coating composition of any one aspects 1 to 17,wherein the coating composition comprises from 15 weight % to 93 weight%, or from 30 weight % to 90 weight %, or from 40 weight % to 85 weight%, or from 50 weight % to 85 weight %, or from 60 weight % to 80 weight% of one or more film-forming resins, based on the total solids weightof the coating composition.

Aspect 19: The curable coating composition of any one aspects 1 to 18,wherein the coating composition comprises from 3 weight % to 35 weight%, or from 5 weight % to 32 weight %, or from 10 weight % to 30 weight%, or from 15 weight % to 25 weight % of one or more curing agents,based on the total solids weight of the coating composition.

Aspect 20: The curable coating composition of any one aspects 1 to 19consisting of particles having an average particle size of from 20microns to 100 microns.

Aspect 21: A method of preparing a curable coating composition accordingto any one of aspects 1 to 20, the method comprising: (a) mixing acombination of solid components to form a mixture comprising: i) afilm-forming resin comprising at least two functional groups; ii) acuring agent reactive with the functional groups of i); and iii)vulcanized rubber particles unreactive with (i) the film-forming resinand (ii) the curing agent; (b) melting and further mixing the mixtureformed in (a); (c) cooling the melted mixture; and (d) grinding themixture of solid components to form a solid particulate curable powdercoating composition.

Aspect 22: A multi-layer coating system comprising: (a) a first coatinglayer; and (b) a second coating layer deposited over the first coatinglayer, wherein the first coating layer and/or the second coating layeris prepared from the curable coating composition according to any one ofaspects 1 to 20.

Aspect 23: The multi-layer coating system of aspect 22, wherein thefirst coating layer comprises an inorganic corrosion inhibitingcomponent comprising a transition metal component, an alkali metalcomponent, an alkaline earth metal component, or combinations thereof.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

The invention claimed is:
 1. A curable coating composition comprising:(a) a binder comprising: (i) a film-forming resin comprising at leasttwo functional groups; and (ii) a curing agent reactive with thefunctional groups of (i); and (b) solid vulcanized rubber particlesunreactive with the binder, wherein the curable coating composition is asolid particulate powder coating composition.
 2. The curable coatingcomposition of claim 1, wherein the film-forming resin has a glasstransition temperature (Tg) of at least 35° C.
 3. The curable coatingcomposition of claim 1, wherein the film-forming resin comprises anepoxy resin having at least two epoxide groups and wherein the curingagent is reactive with the epoxide groups.
 4. The curable coatingcomposition of claim 3, wherein the epoxy resin further comprises atleast one hydroxyl group.
 5. The curable coating composition of claim 4,further comprising a second curing agent that is reactive with thehydroxyl group.
 6. The curable coating composition of claim 1, whereinthe curable coating composition comprises at least a first epoxy resinand a second epoxy resin that each independently comprise at least twoepoxide groups and wherein the curing agent is reactive with the epoxidegroups of the first epoxy resin and the second epoxy resin, wherein thefirst epoxy resin has an equivalent weight that is greater than anequivalent weight of the second epoxy resin.
 7. The curable coatingcomposition of claim 6, wherein the first and/or second epoxy resinfurther comprise at least one hydroxyl group.
 8. The curable coatingcomposition of claim 1, wherein the solid vulcanized rubber particleshave an average particle size of up to 85 microns.
 9. The curablecoating composition of claim 1, wherein the solid vulcanized rubberparticles comprise up to 40 weight % of the coating composition, basedon the total solid weight of the coating composition.
 10. The curablecoating composition of claim 1, wherein the vulcanized rubber particleshave a glass transition temperature (Tg) of less than −40° C.
 11. Thecurable coating composition of claim 1, further comprising pigmentparticles.
 12. The curable coating composition of claim 1, wherein thepowder coating composition is completely free of fiberglass.
 13. Thecurable coating composition of claim 1, further comprising a platyinorganic filler, a needle-shaped inorganic filler, or a combinationthereof.
 14. The curable coating composition of claim 1, wherein thecoating composition is completely free of a thermoplastic resin.
 15. Thecurable coating composition of claim 1, wherein the coating compositionfurther comprises an inorganic corrosion inhibiting component comprisinga transition metal component, an alkali metal component, an alkalineearth metal component, or combinations thereof.
 16. A method ofpreparing a curable coating composition comprising: a) mixing acombination of solid components to form a mixture comprising: i) afilm-forming resin comprising at least two functional groups; ii) acuring agent reactive with the functional groups of i); and iii)vulcanized rubber particles unreactive with (i) the film-forming resinand (ii) the curing agent; b) melting and further mixing the mixtureformed in a); c) cooling the melted mixture; and d) grinding the mixtureof solid components to form a solid particulate curable powder coatingcomposition.
 17. The method of claim 16, wherein the film-forming resincomprises an epoxy resin having at least two epoxide groups and whereinthe curing agent is reactive with the epoxide groups.
 18. The method ofclaim 17, wherein the epoxy resin further comprises at least onehydroxyl group.
 19. The method of claim 16, wherein the vulcanizedrubber particles have an average particle size of up to 85 microns. 20.A multi-layer coating system comprising: a) a first coating layer; andb) a second coating layer deposited over the first coating layer,wherein the first coating layer and/or the second coating layer isprepared from the curable coating composition according to claim
 1. 21.The multi-layer coating system of claim 20, wherein the first coatinglayer comprises an inorganic corrosion inhibiting component comprising atransition metal component, an alkali metal component, an alkaline earthmetal component, or combinations thereof.